Sunday, June 23, 2013

A Color Matched 3D Printed Cargo Rack For My Recumbent Trike

In my last post I showed you my newly acquired recumbent trike.  With the new trike I found that I wanted a cargo rack for it as it would come in handy if I should need something quick from my local grocery store not far away.  I have spent the week creating just such an accessory.

I found a rack for my trike online which would have been perfectly fine but if you know anything about me or my blog this simply would not be the way I wanted to go.  I started design work on the cargo rack as soon as I got the trike assembled and tweaked so that it rode and drove the way I liked.  I then grabbed my tape measure, caliper, and note book and gathered measurements of the rear end , seat, and frame of the trike. Then on to spending a lot of hours using my design software to work out the design that was in my head. Burning the midnight oil so to speak.

This photo shows the main components of the cargo rack before final assembly.  On the right of the photo are the two main platform rails with four mounted connectors on each aluminum tube.  The drilling of the tubes to align everything correctly was an effort to be sure but with a little time and a lot of patience I was successful.  The two upper assemblies that look like sling shots are the support arms that mount to and hold the platform up. The lower ends of these assemblies are mounted to points on both sides of the frame near the rear axle. These assemblies have a double metal flange on the bottom for   a nice strong simple mount. The next smaller assembly (middle bottom of photo) are the connectors that mount the platform to the same mounting points used for the seat supports.  The last three tubes on the lower right are the cross tubes that completed the platform assembly.

Here the cargo rack is fully assembled and ready to be mounted on to the trike.  I wanted the aluminum tubing to be black as this would match nicely with the rest of the trike but I also knew that to paint aluminum was not the way to go.  Instead I wrapped the tubes with black vinyl that had a sticky back to it. This worked out perfectly and if the covering should every get damaged it is just a matter of peeling off the old vinyl and putting new on again.

The entire cargo rack is assembled using standard 10-24 hardware and only took me around ten minutes to mount it on to the trike.  This is where all the planning and computer time paid off.  Gotta love it when a plan comes together first time out.

All of the yellow components of the 10 x 14  inch cargo rack were printed using my 3D printer with  a 25% fill.  Normally when I make 3D printed parts I only use a 10% fill.  To explain this further all parts on a 3D printer are not printed solid.  This would be a 100% filled part.  Instead the parts are made with a lesser fill percent to save plastic and time. Most of the time 10% fill is more than enough to make the part strong enough for the project you are making. When the parts are printed it looks like a honeycomb inside to give the part strength instead of just having a hollow part which would be a very weak part. The percentage of fill I use depends on the strength of the part that is needed for an assembly.  With this  project I thought 25% fill would do the trick.  This made the parts very strong and the entire assembly should hold more weight than I would every want to haul on the trike.  Speaking of weight the cargo rack only added an additional pound and a half to the trike.  This was icing on the cake as the rack only cost me around $28 to design and build compared to close to $70 for a factory model.  As usual with all of my designs and projects bragging rights are priceless!

I figure the heaviest thing that I would bring home for the grocery store would be a gallon of milk. This comes in at 8 lbs 11 oz.  Not a terrible amount of weight but still heavy enough.  I want to work on a cargo box that will attach to the cargo rack.  The one stipulation with the box though is that I want to be able to remove it when I am just out riding my trike for the fun of it.  Why carry along dead weight if I don't have to?  For now this little cargo rack makes a nice addition to the trike and I can always just strap what I want to carry on it until I figure out a cargo box or trunk for it.

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